feat(h5): support shadow

packages/uni-h5-vite/src/plugins/pagesJson.ts

@@ -105,6 +105,9 @@ ${name}.UniServiceJSBridge = UniServiceJSBridge
 function generateCssCode(config: ResolvedConfig) {
   const define = config.define! as FEATURE_DEFINES
   const cssFiles = [H5_FRAMEWORK_STYLE_PATH + 'base.css']
+  if (config.isProduction) {
+    cssFiles.push(H5_FRAMEWORK_STYLE_PATH + 'shadow.css')
+  }
   // if (define.__UNI_FEATURE_PAGES__) {
   cssFiles.push(H5_FRAMEWORK_STYLE_PATH + 'async.css')
   // }

packages/uni-h5/style/framework/shadow.css

+body::after {
+  position: fixed;
+  content: '';
+  left: -1000px;
+  top: -1000px;
+  animation: shadow-preload 0.1s;
+  animation-delay: 3s;
+}
+
+@keyframes shadow-preload {
+  0% {
+    background-image: url(https://cdn.dcloud.net.cn/img/shadow-grey.png);
+  }
+  100% {
+    background-image: url(https://cdn.dcloud.net.cn/img/shadow-grey.png);
+  }
+}